Skin Patch Uses Sweat to Monitor Health

A soft, flexible skin patch that monitors biomarkers in sweat can determine whether the wearer is dehydrated, measure the person’s blood sugar level and even detect disease. The invention is part of an emerging field of wearable diagnostics.

Human sweat contains many of the same biomarkers as blood; however, analyzing sweat using a skin patch doesn't hurt like a needle stick, and the results can be obtained more quickly.

The first-of-its-kind patch is aimed primarily at athletes, but the flexible electronics device will in all likelihood find a place in medicine and even the cosmetics industry.

The skin patch, described in the journal Science Translational Medicine, is made of flexible material, and is about the size and thickness of a U.S. quarter. The so-called microfluidic device sticks to the forearm or back like an adhesive bandage, collecting and analyzing sweat.

"We've been interested in the development of skin-like technologies that can mount directly on the body, to capture important information that relates to physiological health," said John Rogers, a materials scientist and bioengineer at Northwestern University in Illinois, and one of a number of developers of the skin patch. "And what we've demonstrated here is a technology that allows for the precise collection, capture and chemical analysis of biomarkers in sweat and perspiration."

Color-coded results

The sweat is routed through microscopic tubules to four different reservoirs that measure pH and chloride, important indicators of hydration levels, lactate — which reveals exercise tolerance — and glucose. It can also track the perspiration rate.

The skin patch could potentially be used to diagnose the lung disease cystic fibrosis by analyzing the chloride content in sweat. Wireless electronics transmit the color-coded results to a smartphone app, which analyzes them.

To test the patch's accuracy and durability, scientists studied it in two different groups of athletes. One group used an indoor cycle and the other group participated in a long-distance bicycle race called the El Tour de Tucson in Arizona's arid desert. The sweat patch was placed on the arms and backs of the subjects.

Researchers compared the four biomarker results of the indoor athletes to conventional blood tests and found the results were the same.

With the outdoor long-distance cycling group, scientists wanted to test the sweat patch's durability. They found that the electronics device stayed adhered to the athletes' skin, didn't leak and provided the same accurate information as blood tests.

Not just for athletes

For now, the skin patch is intended for use by sweaty athletes to measure biomarkers of performance, and Rogers sees the patch being sold with sports drinks; but, he said, a number of industries have expressed an interest in the sweat-based technology.

"Cosmetics companies are interested in sweat using these devices in their research labs to evaluate their antiperspirants and deodorants and so on,” Rogers said. “So sweat loss and sweat chemistry is interesting in that domain, as well. And then we have contracts with the military that are interested sort of in continuous monitoring of health status of war fighters."

Rogers says he thinks the inexpensive, disposable skin patches should become available to consumers in one to two years.